Automatic and semi-automatic firearms require manipulation of the next cartridge. The manipulation normally occurs through springs applying a force against the cartridge. Opening the chamber to eject a shell or spent cartridge stores energy in the slide spring and the magazine spring to a point where the springs release to “kick” a fresh cartridge into place. This type of mechanism, which is found in most semi-automatic firearms, lacks a positive grip on the cartridge, and usually has a feeding ramp in front of the cartridge, leading to numerous cartridge handling errors made more acute as the springs degrade.
One of these errors is known as a “feed ramp jam”, where the bullet tip stops against the feeding ramp surface, preventing the bolt from fully reaching battery position. Self-defense bullets, such as hollow-points are more prone to feed ramp jams due to their sharp corners on the tip.
Another error is incurred when the cartridge gets ahead of the extractor so that the slide will not fully go into battery.
Another error is known as “rim-lock”, where cartridge rims catch on each other in the magazine, which stops the slide from reaching its battery position.
Yet another error, known as “failure to extract”, is where the spent case remains in the chamber after ignition. It can be caused by percussion gases making the extractor lose its grip on the cartridge.
Another drawback of traditional feed systems is that they leave little room for the barrel. Short barrels do not provide enough burn time for propellant inside of the barrel, so instead the propellant burns on the outside, significantly increasing muzzle flash and noise. Short barrels also reduce bullet energy.
The most common cartridge feeding system is depicted in Hiram Maxim's 1885 U.S. Pat. No. 317,162, where positive control of the cartridge is not exercised.
Past examples of controlled or “positive” cartridge manipulation include U.S. Pat. No. 395,791 to Hiram S. Maxim dated Jan. 8, 1889. However, its design was bulky and not a practical solution for smaller weapons such as pistols.
Another example is GB Pat. No. 25,656 dated Sep. 27, 1906 to Mars Automatic Pistol Syndicate discloses a “pull-back”-style mechanism in a pistol. However, the gun's feed mechanism did not positively control the cartridge at all times, nor did it have means of arresting or trapping the upward motion of the cartridge to prevent feed failures.
Blow-forward feeding systems maximized barrel length, but never implemented positive cartridge manipulation. One example is U.S. Pat. No. 580,935 to C. J. Ehbets on Apr. 20, 1897.
Rotating barrel weapons have not taken advantage of the barrel rotation to lock the extractor closed during ignition. One example of a rotating barrel gun without extractor-locking is found in U.S. Pat. No. 4,984,504 to Pier G. Beretta on Jan. 15, 1991.
What is needed is a compact cartridge feeding system that eliminates the need for the front feed ramp of traditional cartridge feeding systems, and benefits from the positive nature of rearward-feeding systems that grasp a cartridge from the magazine, controls its motion at all times, and does not release it until during ejection from the firearm. What is also needed is a feeding mechanism that maximizes barrel length. What is additionally needed is an extractor that locks against the cartridge rim during ignition.